Differential interlock for a yarder or skidder



March 24, 1970 w. R. HAMERSLEY 3,502,302

DIFFERENTIAL INTERLOCK FOR A YARDER OR SKIDDER Filed June 26, 1968 69 FL 0/0 SUPPLY Walter R mersley,

Lyle G. Trorey,

Agent United States Patent DIFFERENTIAL INTERLOCK FOR A YARDER OR SKIDDER Walter R. Hamersley, Sayward Post Office, British Columbia, Canada Filed June 26, 1968, Ser. No. 740,333 Claims priority, applicationsgnei; Britain, June 28, 1967, Int. Cl. B6611 1/26; F16h 1/40 US. Cl. 254185 6 Claims ABSTRACT OF THE DISCLOSURE Differential means operatively connected to drive a haulback drum at a constant speed or, with a differential element being rotated, at a determinate varying speed giving a variable r.p.m. ratio between the haulback drum and a mainline drum to control line tension. Clutch means releasably interconnecting the differential to the haulback drum, clutch means releasably interconnecting the haulback drum with a bull drive gear, and clutch means for reverse direct drive of the haulback drum with the differential clutch released.

BACKGROUND OF THE INVENTION The invention is a differential interlock for a yarder or skidder.

The use of such devices is now described in general terms with reference to a particular kind of operation. In the rain forests of the Pacific Northwest forest area of North America, logging is commonly effected by high lead means, including a carriage suspended upon a cable running between spar trees. The carriage, and a load thereto attached, are transported by hauling a main line cable secured to a winding drum. A haulback cable, cooperating with a haul-back drum of the yarder is also secured to the carriage, and constructed and arranged so that winding the haul-back moves the carriage in an opposite direction along the suspended cable.

It is desirable that the mainline cable and the haul-back cable be wound and paid out at the same lineal speed. This involves problems well known in the art, and arising from change in effective diameter of the haul-back and winding drums according to the number of layers of cable upon the said drums. Accordingly, each has to be driven at a different instantaneous speed and, moreover, the ratio of the rpm. of the main drum to the haul-back drum continually changes due to the changes aforesaid in effective drum diameters. Further problems arise from the desirability of maintaining a particular and/or a variable tension on the haul-back cable whilst winding the main cable, and vice versa. The problems above briefly indicated have received attention from many inventors, and ingenious and at least partially effective mechanisms have been devised to overcome or at least to reduce the above mentioned difficulties, Particularly, a solution involves the use of a differential drive between the mainline drum and the haul-back drums, in combination with two or three friction clutches transmitting a turning moment to each drum.

OUTLINE OF THE INVENTION The present invention provides drive of the haul-back drum by a gear train including a differential having an outer housing which can be fixed, reversable variable speed drive means being provided to rotate the housing. With the housing fixed, the haul-back drum is driven at a speed dependent only upon r.p.m. of a prime mover, as also is the mainline drum. With the housing fixed, there thus is a constant ratio between r.p.m. of the haul-back drum and r.p.m. of the mainline drum, the ratio suitably being unity. The ratio, being unity, is made to be greater than or less than unity according to direction of rotation of the housing. The ratio, whether it be greater or less than one, has a numerical value dependent upon speed of rotation of the housing. It will be understood by those skilled in the art that means as aforesaid are effective to control effective diameter and line tension.

Clutch means are provided to disengage the differential with additional clutch means cooperating with gear means to drive both drums independently of the differentialand at a constant r.p.m. ratio. In this mode direction of rotation of the haul-back drum is reversed com-pared to differential drive, and tension is controllable as in some previous equipments by means of the clutches.

DESCRIPTION OF THE DRAWINGS FIGURE 1 is a partly sectioned plan view of apparatus according to the invention,

FIGURE 2 shows one means of driving a differential housing.

The drawings are diagrammatic.

A detail description following is relating to the drawing which show exemplification of the invention which, however, can be expressed in structure other than that particularly described and illustrated.

DETAIL DESCRIPTION Description related to FIGURE 1 A differential interlock for a logger or skidder apparatus is designated generally 10 in FIGURE 1. The apparatus has a frame having spaced parallel inner and outer walls 11 and 12. A main line drum 13 is mounted for rotation upon a transverse mainline shaft 14 secured in the frame walls, and a haul-back drum 15 is mounted for rotation on a haul-back shaft 16 secured in the frame Walls, the said shafts being in parallel spaced relationship to one another.

A differential designated generally 17 has a hollow outer shaft 18 and an inner co-axial shaft 19, the hollow shaft being journalled in a hollow shaft journal 21 of the inner frame wall 11. An outer end 22 of the inner shaft 19 is journalled as seen at 23 in the frame outer wall 12, the inner shaft being parallel to and disposed between the main line and haul-back drums. A differential drive pinion 24 is secured at an outer end 25 of the hollow shaft as seen at 26, a driven bevel gear 27 being secured as seen at 128 to an inner end 29 of the hollow shaft. An inner shaft bevel 31 is secured to the inner shaft 19 as seen at 32, intermediate bevel gears 33 and 34 mounted on short aligned shafts 35 and 36 of a housing 37 of the differential engage the driven bevel 27 and the inner shaft bevel 31. Thus, with the housing 37 being fixed, rotation of the differential drive pinion 24 rotates the inner shaft 19 at a speed determined by pitch diameter ratios of the bevel gears.

A bull gear 38 is rotatably mounted on the mainline shaft 14 between the frame inner Wall 11 and an inner flange 39 of the haul-back drum 13. A mainline clutch 40 has a driving element 41 secured to a face of the bull gear 38, and a driven element 42 secured to the inner flange 39, the clutch being constructedand arranged so that, when engaged, the mainline drum rotates on the shaft 14 with the bull gear. The clutch 40 is, as are other clutches later to be described, of a known type commonly used in yarders and skidders. Means of engaging and disengaging the clutch (not shown) are well known to those skilled in the art and, therefore, are not described. The engaging and disengaging means of the clutch 40, and of the other clutches aforesaid, include hand controls (not shown) conveniently placed for use by an operator of the apparatus.

The bull gear 38 is in operative engagement with the differential drive pinion 24 of the hollow outer shaft 18, so that rotation of the bull gear also drives the pinion 24.

The bull gear 38 is driven by prime mover means, not shown, in any convenient manner as well known in the art, and the driving means can include reversing means so that the bull gear can be driven in either direction at will.

An interlock pinion 43 is secured to the inner shaft 19 adjacent the frame outer wall 12 as seen at 44, interlock gear 45 engaging the interlock pinion is mounted for rotation on the haul-back shaft 16 between an outer flange 46 of the haul-back drum and the frame outer wall 12 as shown.

A haul-back interlock clutch 50 has a driving element 51 secured to a face of the interlock gear 45 rotating therewith, a driven element 52 being secured to the outer flange 46 aforesaid. The clutch 50 is as before described with reference to the clutch 40, the clutch 50 being adapted, when engaged, to cause the haul-back drum to rotate with the interlock gear 45.

A haul-back gear 53 is mounted for rotation on the haulback shaft 16, the haul-back gear engaging the differential drive pinion 24 so as to be driven thereby, the haul-back gear being mounted between an inner flange 54 of the haul-back drum and the .frame inner wall 11.

A haul-back clutch 60 has a drive element 61 secured to and rotating with the haul-back gear 53, and a driven element 62 secured to and rotating with the inner flange '54 of the haul-back drum, the clutch 60 being adapted so that, when engaged, the haul-back drum 15 is driven by the haul-back gear 53 the clutch 50 being disengaged. The clutch 60 is as before described with reference to the clutch 40.

Means to rotate the differential The inner shaft 19 extends through the differential housing 37, the shaft having an end 63 opposite the end 22 aforesaid. The shaft end 63 is journalled as seen at 64 in outer supporting structure 65 surrounding the differential, which supporting structure is rigidly secured to the frame inner wall 11 as seen.

A ring worm gear 67 is secured to the differential housing 37, the worm gear being co-axial with the inner shaft 19. A worm 68 cooperates with the worm gear 67 so that rotation of the worm rotates the differential Housing 37.

FIGURE 2 shows the worm 68 secured to a shaft of a variable speed reversible hydraulic motor 69, of a known kind. The hydraulic motor has conventional controls, not shown, so that the operator can at will cause the differential housing to rotate in one direction, or in an opposite direction, at any speed within the range of the motor, or to cause the differential housing to remain stationary.

OPERATION It is seen that with the haul-back interlock clutch 50 disengaged, and the mainline clutch together with the haul-back inner clutch 60 engaged, the mainline drum 13 is directly driven at the speed of rotation of the bull gear, and that the haul-back drum is also directly driven at the speed of rotation of the haul-back gear 53. As described and illustrated, the mainline and haul-back drums rotate in the same direction. The drive is then independent of the differential and, when the bull gear and haul-back gears are of the same pitch diameter, speed of rotation of both drums is the same with their directions of rotation the same. This is a normal means of operation of art yarders and skidders, with control of drum rotation being effected by the clutches 40 and 60.

With the mainline clutch 40 and the haul-back interlock clutch engaged and haul-back inner clutch being disengaged, drive of the mainline drum is still direct but drive of the haul-back drum is now through a gear train including the differential 17, through the inner shaft 19, the interlock pinion 43, and the interlock gear 45.

With the differential housing 37 stationary, as is the case when the hydraulic motor 69 is stopped, there is a constant ratio between the speed of rotation of the mainline and haul-back drum, which ratio can be one to one or can be otherwise as desired, according to pitch diameters of the several cooperating gears and pinions.

With contant speed of the bull gear and consequently of the mainline drum 13, the instantaneous ratio of r.p.m. of rotation of the haul-back drum to that of the mainline drum can be changed by rotating the differential housing 37. The speed of rotation of the haul-back drum will be greater than, or less than, that of the mainline drum according to the direction of rotation of the differential housing, that is to say of the variable speed motor 69; and the ratio of r.p.m. of the haul-back drum to r.p.m. of the mainline drum is a function of the speed of rotation of the housing. It is thus seen that the ratio of r.p.m. of the haul-back drum to that of the mainline drum is continuously variable within wide limits. Thus, the main drum rotating in a direction to haul in the mainline, the haulback line is played out off the haul-back drum at such speed as is required to maintain a desired tension. If the direction of rotation of the bull gear 38 is now reversed, the haul-back line will be pulled in winding on the haulback drum, and the mainline will be paid out off the mainline drum. As before, tension is controllable by variation of speed and direction of rotation of the housing.

The combination of the three clutches and the gearing and differential provides; direct drive of both drums, independent of the differential, at a constant r.p.m. ratio both drums rotating in the same direction, when tension control can be effected by the clutches; direct drive through the differential with the differential housing fixed, direction of rotation of the mainline drum being opposite to that of the haul-back drum, and with tension control possibility by means of the clutches as before; drive through the differential with the ratio of the r.p.m. of the haulback drum to r.p.m. of the mainline drum continuously variable from a value greater than one, through less than one by rotation of the differential housing as hereinabove explained in detail, so effecting control of tension without slipping a clutch.

EQUIVALENT CONSTRUCTIONS One means of rotating the differential housing at continuously variable speed in either direction, or to hold the housing fixed, has been described and illustrated. The worm drive and hydraulic motor means is simple. Alternatively, power from the prime mover can be used, with for instance a known variable speed torque converter and reversing gear means, final drive being either by worm or by a reducing train. Electrical drives effecting variable speed in either direction are also known and can be used equivalently.

The particular means used to effect rotation of the differential housing is not important, it is required only that means, any suitable means, he provided to effect reversible rotation of the housing at a continuously variable speed.

A particular differential configuration has been described and illustrated by way of example. Other differential trains can be substituted, it being required that the haul-back drum can be driven through the differential, with means being provided that a differential element can be fixed, for constant speed drive of the drum-the differential being driven at constant speedand means to rotate the fixed element adapted for variable speed ratio between the differential drive and the drum. That is to say, the particular differential drive used is unimportant provided that the differential is adapted to function as aforesaid.

I claim:

1. A differential interlock for a yarder or skidder apparatus having a frame with spaced inner and outer walls, a mainline drum mounted for rotation about a transverse mainline shaft of the frame and a haul-back drum mounted for rotation about a haul-back shaft of the frame, the mainline and haul-back shafts having secured in the frame walls in parallel spaced relation to one another, in combination:

(a) a differential having a hollow outer shaft, and an inner shaft eXtending'co-axially through the hollow shaft, with the hollow shaft being journalled in a hollow shaft journal of the frame inner wall, and an outer end of the inner shaft being journalled in the outer wall of the frame, a differential drive pinion being secured to an inner end of the hollow shaft, a driven differential bevel gear being secured to an inner end of the inner shaft, an inner shaft bevel gear secured to the inner shaft and spaced from the drum bevel aforesaid, adapted for rotation of the differential drive pinion to rotate the inner shaft,

(b) a bull gear mounted for rotation on the mainline shaft between the frame inner wall and an inner flange of the mainline drum, and prime mover means to drive the bull gear,

(c) a mainline clutch releasably interconnecting the mainline drum to the bull gear, adapted so that the mainline drum is driven by the bull gear when the mainline clutch is engaged,

(d) a hollow shaft pinion in operative engagement with the bull gear, said pinion being secured to the hollow shaft, so that the differential drive pinion is driven by the bull gear,

(e) an interlock pinion secured to the inner shaft, and

an interlock gear mounted for rotation on the haulback shaft, the pinion being in engagement with the interlock gear,

(f) a haul-back interlock clutch releasably interconnecting the haul-back drum to the interlock gear so that the drum is driven by the interlock gear,

(g) the differential having a housing and means to effect reversible rotation of the housing at a continuously variable speed, so that with the mainline and haul-back interlock clutches engaged, and the differential housing stationary, the haul-back drum is driven at a speed bearing a constant ratio to that of the bull gear, said ratio being variable according to a speed at which the differential case is rotated by said means.

2. A combination as defined in claim 1, and

(h) a haul-back gear mounted for rotation on the haulback shaft with the haul-back gear in operative engagement with the hollow shaft pinion,

(i) a haul-back inner clutch releasably interconnecting the haul-back gear and the haul-back drum, so that with the haul-back inner clutch disengaged the haulback drum is driven as aforesaid, and so that with haul-back interlock clutch disengaged and the inner haul-back clutch engaged, the haul-back drum is driven independently of the differential in an opposite direction.

3. A combination as defined in claim 1, the means to rotate the housing including; a worm gear secured to the housing concentric with the inner shaft, worm means engaging the worm gear, and reversible variable speed power driven means to rotate the worm.

4. A combination as defined in claim 2, the means to rotate the housing including; a worm gear secured to the housing concentric with the inner shaft, worm means engaging the worm gear, and reversible variable speed power driven means to rotate the worm.

5. A combination as defined in claim 1; the mainline clutch having a drive element secured to a face of the bull gear and a driven element secured to the mainline drum inner flange; the haul-back interlock clutch having a drive element secured to the haul-back gear, and driven element secured to an outer flange of the haul-back drum.

6. A combination as defined in claim 2; the haul-back inner clutch having a drive element secured to the haulback gear and a driven element secured to an inner flange of the haul-back drum.

References Cited UNITED STATES PATENTS HARVEY C. HORNSBY, Primary Examiner US. Cl. X.R. 747l3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 502 3Q2 Dated 29 March 1370 Inventor-(s) Walter HAMERSLEY It is certified that error appears in the above-identified-patent and that said Letters Patent are hereby corrected as shown below:

r a "I In claim 1. 001.5 line 2 [having] is deleted and m entered; line 11 [inner] is deleted and g u te: entered; line 14 inner} is deleted and hollow entered and in the same line [drum] is deleted and driven entered; line 43 [case] is deleted and housing entered.

In claim 5. Col. 6 line 27 [haul-back] is deleted and interlock entered.

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